The demands on braking devices for motor vehicles are continuously rising. Currently, requirements are no longer only placed on the performance and reliability of brakes, but rather the braking modes to be controlled, and other functions of brakes, for example, in the dynamic vehicle support, are becoming ever more complex.
Fundamentally, modern vehicles have multi-circuit brake systems, which, on the one hand, have multiple brake circuits or groups of brake circuits for redundancy, and, on the other hand, also allow brake circuits to be controlled individually, in order to distribute the brake force advisably to the brake circuits.
Within an individual brake circuit, brake governors at individual wheels may also provide varying brake force distribution to the wheels. Typical brakes on wheels of vehicles are, for example, disc brakes or drum brakes, fundamentally brakes acting on the basis of friction in any case. In addition, however, another assembly may also be used for the deceleration of wheels, such as typically an engine brake, which may be regulated in turn by appropriate settings on an internal combustion engine, or a generator. In a motor vehicle, either the typically provided small generator in the form of a dynamo comes into consideration as the corresponding generator, which is used for charging the starter battery and for supplying the electrical systems of the vehicle, or, in the case of a hybrid vehicle, a drive motor, which may be operated as a generator and may then be used for charging the drive battery, for example. Similar vehicles which are operable alternatively electrically or with the aid of an internal combustion engine are called hybrid vehicles. The action of reclaiming energy during a brake application using a generator and thus braking the vehicle is referred to by the term recuperative braking.
Fundamentally, optimizing the driving safety and brake application in a vehicle by suitable control or regulation of individual brake circuits or brakes and the employed braking arrangement is understood.
Thus, a brake pressure regulation system for a vehicle is discussed in DE 4128087 A1, using which an underbraked rear axle is prevented in the case of braking while cornering. The brake pressure on the front axle is specified by the driver, and the brake pressure on the rear axle is regulated as a function thereof.
Distributing the brake force in such a way that the strongest possible braking of the vehicle is achieved in consideration of the friction utilization is also known, wheels which are more heavily loaded statically and/or dynamically also being able to be more strongly affected by the brakes.
A system is discussed in EP 0173954 B1, in which the brake pressures for individual brakes are ascertained using a reference mass for the vehicle and the setpoint deceleration, which is specified by the driver, in a stored vehicle-specific characteristic map. The ascertained brake pressures are introduced into the brakes and readjusted as needed in the event of deviation of the vehicle deceleration from the setpoint value until the setpoint deceleration is achieved.
A brake pressure regulating unit is known from DE 3313078 A1, which ascertains and takes into account the wear of various wheel brakes, so that a more uniform wear of the individual wheel brakes is achieved in the long term.
A brake system is known from DE 102005046606, in which one brake circuit is associated with each of the axles of a vehicle, so that an anti-slip unit and a vehicle dynamics controller may be provided exclusively in one brake circuit, whereby the total design expenditure is minimized.
Finally, from DE 10316090 A1, a brake system is discussed having multiple brake circuits, which fundamentally work hydraulically and act on friction brakes of individual wheels, and having a generator or an electric drive motor, which is operable as a generator and may additionally be used for deceleration. A control unit is provided to optimize the brake force distribution to all individual wheels in consideration of various vehicle-dynamics variables.